A liquid crystal display panel requires photo spacers (PSs) for supporting a color filter substrate and an array substrate, the photo spacers are used to maintain a distance between the color filter substrate and the array substrate, so as to prevent the thickness of the liquid crystal cell from becoming abnormal.
In general, the bottom of the photo spacer is formed on a surface of the color filter substrate, and the free end thereof is in contact with a surface of the array substrate, the height of the photo spacer forms a level difference. The larger the level difference, the easier it is to affect coating of alignment liquid when forming alignment layers on the substrates (the color filter substrate and the array substrate) (that is, since the surface of the substrate is uneven, the alignment layer formed by coating the alignment liquid will accordingly become uneven, or even has defects), thereby causing light leakage and various mura defects in the display panel. Furthermore, for a curved panel, during bending a display panel from a flat surface state into a curved surface state, thicknesses of respective parts thereof become different inevitably. In other words, the bending process of the display panel may cause the photo spacer to be subjected to different external forces in areas bent to different extents. When the photo spacer is subjected to the external forces due to the bending of the display panel, the photo spacer may shift to left or right, so as to scratch and damage the alignment film at the side of the array substrate, the scratched portion of the alignment film no longer has the alignment function, and therefore, liquid crystals corresponding to the portion can hardly align in a required alignment direction, which causes disorder arrangement of the liquid crystal molecules corresponding to the portion, thereby resulting in light leakage. FIG. 1 is a schematic diagram illustrating a case where light leakage occurs due to a portion of the alignment film 3 on the array substrate 2 corresponding to the G pixel that scratched by the photo spacer. When a R pixel in the color filter substrate 1 is lit up, in a normal case, the color filter layer corresponding to the G pixel cannot transmit light, however, since the portion of the alignment film 3 corresponding to the G pixel is scratched, green light leaks at a position of the color filter layer corresponding to the scratched portion, thus resulting in light leakage in the display panel. In addition, even during the modularized process performed on the display panel, if the display panel is bent due to mechanical failure, the alignment film 3 may be damaged to cause light leakage in the display panel.
In the prior art, there is no effective solution to solve the problem of light leakage and various mura defects in the display panel due to uneven or defective alignment film caused by a level difference formed by the photo spacer. Moreover, in the prior art, in one solution for solving the problem of light leakage in the display panel due to damage of the alignment film caused by the photo spacer: photo spacers having different heights are used at different positions of the display panel, however, even with this structure, the photo spacer may still come into contact with the alignment film when the display panel is bent, and cannot prevent the photo spacer from scratching the alignment film when the display panel is bent.
It can be seen that, designing a liquid crystal display panel free of light leakage and various mura defects has become a technical problem to be solved urgently.